At 08:17 AM 2/9/2004 -0500, you wrote:
>First, I want to thank everyone for their valuable inputs on converting
>PIC outputs to CMOS.  Now, I have found a need to go the other way.
>
>I'd like to convert the output of a 12V 4000 Series CMOS IC to the
>digital input of my PIC16C76 which is running at 5V.

As I suggested earlier, "A 4049/4050 (Vdd=5V) will convert from the 4000
CMOS to PIC. (inverting / non-inverting hex buffer)" This works fast,
does 6 lines with a single part and uses almost zero power.

If you only have one or two lines you can either use a transistor
or resistor (preferably a resistor divider). Let's assume

Eg. 0/15V 4000 CMOS ----[22K]----x---------> To PIC
                                  |
                                 [10K]
                                  |
                                  0V

Note: This circuit should only be used with TTL-level PIC inputs,
not with Schmitt trigger CMOS level PIC inputs.

Using 4-resistor networks you can get 4 lines with two small
parts.

Or get rid of the 10K resistor and depend on the PIC protection diode to
clamp the voltage, but this is not recommended in general- it could cause
a couple of subtle problems.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

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